(1) Field of the Invention
The present invention relates to a rotary wing aircraft provided with an emergency undercarriage. The invention lies in particular in the field of landing gear for rotary wing aircraft, and more particularly rotorcrafts.
(2) Description of Related Art
Conventionally, an aircraft includes landing gear via which it stands on the ground. For example, the landing gear may be provided with three or four wheeled undercarriages constituting a support polygon for the aircraft on the ground. Undercarriages are also known that have skids.
Such undercarriages may be retractable in order to optimize the aerodynamic drag of the aircraft. The most prominent elements of the aircraft are folded into the inside of the fuselage, in particular retractable landing gear. More precisely, each undercarriage is retracted in flight into a compartment conventionally referred to as a landing-gear bay, so as to be ready for deploying when required for landing.
It should be recalled that landing gear may comprise not only main undercarriages close to the center of gravity in order to support a major fraction of the weight of the aircraft, but also auxiliary undercarriages located towards the nose or the tail of the aircraft in order to provide stability and contribute to steering the aircraft on the ground. In this context, an undercarriage arranged near the nose of the aircraft is sometimes referred to as the “nose” undercarriage, whereas an undercarriage arranged near the tail of the aircraft is sometimes referred to as the “tail” undercarriage.
An auxiliary undercarriage is advantageously steerable, unlike a main undercarriage.
Retractable main or auxiliary undercarriages thus present an advantage from an aerodynamic point of view. Nevertheless, like any other system, such undercarriages might be subject to failure, and for example they might remain blocked in their landing-gear bays in flight inside the fuselage in the event of a failure of their deployment system, which failure may be of mechanical, electrical, or indeed hydraulic order.
Under such circumstances, at least one undercarriage of an aircraft may remain blocked in its bay, even though the probability of having several undercarriages blocked simultaneously is low. In the event of failure, recourse is made to palliative means that are effective to a greater or lesser extent.
In a first method that is applicable to an undercarriage having a hydraulic actuator for extending it, the undercarriage can be extended manually in the event of a failure, e.g. by using a manual pump or an electric pump if there is a failure of hydraulic pressure generation.
In a second method, that is applicable to a rotary wing aircraft of the rotorcraft type that can hover close to the ground, an operator may be tempted to extend the undercarriage from the outside. It will be understood that such an operation is risky or even dangerous. This operation is not recommended by rotorcraft manufacturers.
In a third method applicable to a rotary wing aircraft of the rotorcraft type capable of hovering close to the ground, an operator installs tooling on the landing area and the pilot puts the rotary wing aircraft down on the tooling at the time of landing. It is then necessary to have suitable tooling available. Nevertheless, it can be understood that landing is then complicated since the pilot needs to put the aircraft down accurately on the tooling.
In a fourth method, the pilot lands with at least one undercarriage retracted inside the fuselage. This method inevitably leads to damage to the fuselage and thus gives rise to repair costs that are likely to be expensive, even for a helicopter type rotorcraft that is capable of landing very slowly.
In a fifth method applicable with a rotary wing aircraft of the rotorcraft type, such as a helicopter in particular, the pilot lands in a gravel pit provided for this purpose, said pit allowing the aircraft to be put down on a surface that is soft and that matches itself as closely as possible to the shape of the fuselage so as to limit the damage caused by landing.
It can be understood that in the event of an undercarriage failing, it is difficult to land without damaging the aircraft and/or without endangering a person taking action on the outside.
An object of the present invention is thus to propose a rotary wing aircraft provided with a device for facilitating landing of the rotary wing aircraft in the event of at least one undercarriage failing.
It should be observed that it is common practice to use a retractable stand on a motorcycle in order to park the motorcycle. That teaching is remote from the technical field of the invention insofar as the stand of a motorcycle is not required to compensate for a failure to deploy an undercarriage wheel. The stand is essential for parking the motorcycle in normal operation, and as a result it is not used in the event of an undercarriage failing.
Similarly, document GB 1 351 739 discloses a device for stabilizing a trailer while performing loading or unloading operations, and a tractor while performing predetermined work. The teaching of that document GB 1 351 739 is thus remote from the technical field of the invention, since the means described do not have the function of replacing an undercarriage blocked in a bay.
Similarly, the state of the art also includes document U.S. Pat. No. 2,776,148 A, document EP 0 324 683 A1, document U.S. Pat. No. 2,454,611 A, document U.S. Pat. No. 227,747 A, and document EP 0 049 964 A2.
Document U.S. Pat. No. 2,776,148 A relates to a docking station for a trailer, and more precisely a station that supports a front portion of the trailer.
Document EP 0 324 683 A1 relates to means for stabilizing a helicopter having tricycle landing gear used in addition to undercarriages for stabilizing said helicopter on a moving platform.
Document U.S. Pat. No. 2,454,611 A relates to retractable landing gear.
Document U.S. Pat. No. 2,927,747 A describes to landing gear for landing on sloping ground.
Document EP 0 049 964 A2 describes means for supporting a helicopter on a platform.